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- Title
A comparison of resistivity imaging techniques using 1D, 2D and 3D MT inversions in the middle Rio Grande Rift, NM.
- Authors
Folsom, Matthew; Person, Mark; Pepin, Jeff; Peacock, Jared; Kelley, Shari
- Abstract
Twelve magnetotelluric (MT) soundings were collected along a 40 km profile crossing the Rio Grande rift and a portion of the Socorro Magma Body. A comparison of 1D, 2D and 3D inverse models highlight the strengths and weaknesses of the respective methods. 2D inversion results are distorted by the 3D nature of the data at longer periods, producing conductive artifacts at depths greater than 3 km. We demonstrate through a 3D forward modelling exercise how it is possible to recreate this effect by placing large resistive and conductive features off of an otherwise perfectly 2D resistivity model. Investigators that image deep conductors using 2D inversion codes should consider the influence of off-axis 3D features. The models outline the geometry of syn-rift and pre-rift sediments at the "Socorro Constriction", the southern terminus of the Albuquerque Basin. A strong, northward trending conductor 2-3 km deep and less than 2 ohm-m is coincident with the rift, creating a reversal of induction arrow directions at this point. This is interpreted as deep basin brines, perhaps influenced by evaporates hosted in the Permian Abo and Yeso formations. It has been noted that Rio Grande salinity increases in a stepwise manner, coincident with the terminal ends of sedimentary basins. Our geophysical models suggest a possible connection between rift-bounding faults and deep sedimentary brines, which likely impact the water quality of the Rio Grande. Future work includes adding additional MT stations to better constrain off-axis features and their relationship to the Rio Grande.
- Subjects
ALBUQUERQUE Basin (N.M.); RIO Grande Rift; MAGNETOTELLURIC prospecting; GEOLOGIC faults; WATER quality; SALINITY; THREE-dimensional imaging in geology
- Publication
New Mexico Journal of Science, 2016, Vol 50, Issue 1, p72
- ISSN
0270-3017
- Publication type
Article